Precious metals are used in a variety of industrial applications including in electrical circuits as electrical contact surfaces, conducting paths and heat sinks. Various properties of precious metals make such applications highly advantageous. These properties include physical and chemical stability, high electrical conductivity and high thermal conductivity. Precious metals are often used in high-density circuits such as integrated circuits because of one or more of the properties set forth above. Gold is used extensively in these applications with great success. However, the high price of gold and the rapid fluctuations in the price of gold makes it attractive to consider other precious metals for some of the applications where gold is traditionally used.
For many of the applications outlined above, palladium and palladium alloys may be highly useful. Because of chemical inertness, reasonable hardness and good wear characteristics, palladium is especially attractive as an electrical contact material in electrical connectors, relay contacts, switches, etc. Various palladium alloys such as palladium-silver, palladium-nickel, and palladium-copper are also useful for the same applications. Indeed, because of the increasing cost of gold, palladium and palladium alloys become more and more attractive economically as a contact material, surface material and in other applications.
A particularly difficult problem in palladium electroplating processes is selection of a suitable palladium compound to supply palladium initially to the bath and replenish the bath as palladium is used up. The compound should be stable, easily made in reasonably pure form and readily soluble in the electroplating bath. The problem is particularly difficult where rapid, high quantity palladium electroplating is being carried out. In this case, relatively large amounts of palladium metal are being plated out and therefore large amounts of palladium must be added to the bath. Under these circumstances, high solubility and high rate of solubility is extremely important. In addition, compatibility of the components of the palladium compound (complexing species, anion, etc.) is also of much practical importance since it might limit the lifetime of the electroplating bath and alter the electroplating characteristics of the bath.
A variety of procedures have been used to electroplate palladium, including the use of various aliphatic polyamine compounds as complexing agents in the electroplating process.